Potentiometer with removable control shaft

ABSTRACT

A potentiometer element housed in an anchoring body which is provided at the extremities of its walls with a plurality of lugs which are deformable angularly in order to hold the potentiometer element, also incorporating a control shaft wherein the insertion extremity of the shaft presents a groove which forms two elastic lugs which, when brought closer to each other permit the removal and replacement of said control shaft. The potentiometer element is also characterized in that, in the system of contacting the resistive track with the ends of the corresponding terminals, there are provided two or more protuberances which act as springs, and terminals present a notch so as to facilitate the bending and to reduce the recovery effect.

FIELD OF THE INVENTION

The present description relates, as indicated in its title, to animproved potentiometer also know as adjustment semi-drive potentiometerintended for use preferably in electronic circuits.

BACKGROUND OF THE INVENTION

In the present state of the art certain potentiometers are known, whichin some cases have a housing in which they ore located and retained bymeans of a plange which provides the fixing of the unit to itscorresponding support or base by means of a pin having a threadedportion at its outer surface, while inside of said pin slides a shaft,which is attached to the pointer and through the activation thereof,allows for the desired adjustments of said potentiometer. Thesepotentiometers, use the process of bending the ends of terminals overthe coinciding ends of resistive plate in order to provide contactbetween said terminals, whereby in order to obtain the desired contact aconsiderable pressure is to be exerted thereupon. The collector of thepotentiometers to which reference is being made, incorporate at acentral point thereof a cylindrical shape provided for guiding the endof the pointer carrier, said cylindrical shape being formed by means ofbending and pressing the material towards outside. In other cases, saidcylindrical shape is obtained simply by a punching action. Further, tobe mentioned as a constructive element in the known potentiometers isthe flanging of the pointer carrier over the collector thus allowing forthe sliding and guiding of said pointer carrier.

The aforementioned potentiometers have the problem of not having auniform and reliable rigidity or absence of movement between thepotentiometer as such and the housing in which it is located, becausethe perimetral flanging for fixation requires a highly controlledpressure, in order to avoid, in some cases, deformation of the element,and in others, to provide an ostensible clearance. Iqually to theprevious case, the flanging of the pointer carrier turns out to besomewhat troublesome because if the pressure applied is not sufficient,clearances would be formed, whereas if said pressure is too strong, anexcessive friction with the cylindrical shaped collector which wouldcause difficulty in the sensibility of the adjustment of the rotor andthe pointer over the resistive track. Also, obstruction in the rotationof the pointer carrier may be caused by the presently existingoperations for drilling the collector as in the case of bending, thepoint of stretching may suffer breakage which obviously dampers aregular sliding of the pointer carrier, whereas in the case said drilledportion is punched, rough edges are logically produced which undisreablydamper the uniform rotation of the pointer carrier.

Another problem which the present potentiometers have is that if thecontrol shaft is damaged, it cannot be substituted and the completepotentiometer would be thrown away.

The bending or nipping which presently is practiced for transmitting theelectric energy by contact between the resistive track and theassociated terminals thereof presents the drawback of producingintermittent losses of electric continuity because the system used forbending the lug permits a logical recovery of the material which tendsto loosen off from the opposing contact surface. In the case ofattempting to avoid the aforementioned loosening off by applying ahigher constant force in the bending, one faces the risk of obtainingexcessive deformations which damage the element.

SUMMARY OF THE INVENTION

In order to overcome the aforementioned problems, the improvedpotentiometer object of the present invention is proposed, which isconstituted by three clearly differentiated elements which are apotentiometer element, an anchoring body and a control shaft.

The potentiometer includes a squared shape body of variable height,inside which a resistive track is inserted and remains firmly stapled tothe aforementioned body due to a pressure exerted by bent over lugswhich correspond to the extremity of terminals of the same, which inturn are intended to contact with the mentioned resistive track in orderto transmit a regulated electric energy. The aforementioned constantpressure is obtained by means of bent lugs, which in order to avoid theeffect of recovery after the bending have incorporated a notch preciselyat the point intended for bending. Also in order to maintain theconstant pressure between the resistive track and the bent ends of theterminals, a number of slight protuberances cooperate which are locatedat the bottom of the body, precisely coinciding with the zone of theresistive track corresponding to the stapled portion of the terminals,such that when the programmed pressure is exerted in order to effect thebending of the lugs of the terminals over the ends of the resistivetrack, the latter logically transmits its pressure to the protuberances,which yield a variable height which is later recovered in its majorpart. Thus, by being minimal the recovery of the bent portion of theterminals, a spring type effect is obtained with the protuberances whichassure a constant pressure between the resistive track and theassociated terminals. The pointer remains inserted in the pointercarrier due to the corresponding guides which the latter has, assuringalso immovability due to an incisive design of the angles of the lugsintended for interlocking of the same. The pointer carrier rotor isattached to the body or housing at a lower part thereof, 3 or morenotches or riveting points have been provided, which facilitates acontact and regular sliding of the pointer both in relation to thecollector, and to the resistive track. The collector of laminerconstitution has a central hole which is designed such that, by means ofa stamping or pressing of the material it is possible to form at thelower part thereof a bevelled portion, while at the upper part thereof acircular profile is extended which ends at a radius which coincides atthe inner part thereof with the shape of the drilled portion, whereas atthe outer part, said radius coincides with an inclined line which fallsof the external base of the collector.

The anchoring body at the zone where the potentiometer is situated, hasa squared-shape configuration, having as extended portion of its walls aplurality of lugs, which by being bent towards inside due to plasticdeformation, assure the fixing of the potentiometer. Also in the fixingof the potentiometer inside the anchoring body, various concavecurved-shape notches cooperate with inner convex curved-shape salientswhich correspond, as it is understood, to the housing of thepotentiometer and the anchoring body, in both cases towards the upperpart thereof. One side of the aforementioned squared-shape anchoringbody has an opening in the form of a window, which is intended fordisplaying the printing corresponding to the model or thecharacteristics of the element. Opposit to the potentiometer andcentrally situated with respect to the latter, the anchoring bodycontains a cylindrical body having two different inner diameters, thelower diameter intended for guiding the control shaft, while between thelarger diameter and the control shaft a cavity is formed in whichcertain amount of lubricating grease is placed. The outer diameter ofthe mentioned cylindrical body has a threaded portion which allows forsecuring the potentiometer to the plate or the base upon which it islocated.

The control shaft at the end where it is inserted in the potentiometer,has a device in the form of an elastic clip, capable of retaining theshaft inside its housing as long as use is not made of a suitable toolfor acting upon the elastic part which yields for permitting the takingout of the mentioned shaft.

The improved potentiometer herein presented has multiple advantages overthe ones presently known, from which the main improvement to highlightis that of the system of stapling of the terminals to the resistivetrack as described hereinabove, which provides that electric corrent istransmitted from the resistive track to the terminals in a stable anddropless manner since the pressure exerted by the protuberances of thebody over the resistive track is performed in a continuous and regularmanner which does not damage the resistive track.

Also contributing to the stability of the pressure of the staplingbetween the terminals and the resistive plate, is the system of bendingthe ends of the terminals, which due to a bent notch assure a minimalrecovery after pressing. As a consequence of the stability of thestapling of the terminals and the aforementioned resistive track one canachieve to reduce to a minimum the defects of contact produced byexpansion during welding the potentiometers by wave bath or othersystems.

Another advantage provided is the rigid emplacement of the pointer overthe pointer carrier rotor, obtained by the blocking lugs of the pointerwhose end angles terminate in an incisive form in order to be insertedin its housing in the rotor.

This firmness between the rotor and the pointer contributes in providingto the potentiometer a better precision in relation to its adjustment,thus obtaining the same resistive valve at any point on the resistiveplate irrespective of whether the rotor-pointer assembly rotatesclockwise or counterclockwise.

Also as a significant advantage the guiding system of thepointer-carrier rotor inside the central drilled portion provided in thecollector is to be mentioned, which due to its designs, allows for aregular rotation as the pressure existing between the neck of thepointer carrier rotor and the drilled portion guiding the same is veryslight. The system of fixing the rotor to the collector with three ormore points of riveting by plastic deformation also contributes toproviding a smooth and regular sliding movement of the rotor-pointerassembly, thus avoiding variations in the rotational torque of thepotentiometer. Also it is to be mentioned that the operation of fixingthe pointer carrier rotor to the collector by riveting of three or morepoints through plastic deformation is easier to be carried out than atotal flanging thus obtaining an economic saving both in tools andproduction time.

Another advantage provided by the present invention is derived from theparticularities of the anchoring body, as it contains a window oropening in one of its walls, provided so as to make possible to seeprinted code or characteristics of the potentiometer.

Another advantageous particularity of the anchoring body consists of acavity intended for placing a lubricant grease therein, said cavitybeing provided in the drilled portion where the control shaft passesthrough, thus the latter has a smooth and uniform rotation due to thelubricant element. The system of fixing the potentiometer element insidethe anchoring body presents another important advantage over the knownmeans which use flanging, as the gripping system by means of multiplelugs or ribs which are bent through plastic deformation, as well as thelateral notches assure immobility between the two pieces, while at thesame time a minimal and necessary pressure is exerted which not capableof causing deformations to the assembly.

Another advantage over the known means is that the control shaft isdismountable in the case of damage or deflect, thus giving rise to animportant saving in waste of manufacture as well as in relation to theuse which by simply substituting the control shaft would avoid the useof a new potentiometer.

Finally as another advantage it is mentioned that one may use anadjusting potentiometer as a control potentiometer of low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the object of the present invention, apreferred practical embodiment of the same has been represented in anextended manner in the accompanying drawings in which;

FIG. 1 shows the improved potentiometer cross-sectioned.

FIG. 2 shows a detail of the cross-section of the central register ofthe collector.

FIG. 3 shows a detail of the cross-section of the rotor-pointer assemblyanchored to the collector.

FIG. 4 shows an upper view of the anchoring lugs of the rotor to thecollector.

FIG. 5 shows an upper view of a detail of the cursor.

FIG. 6 shows a cross-section of the pointer anchored to the rotor, wherea stage prior to the pressing which gives rise to the insertion of thelugs of the pointer inside the lodging of the rotor in broken lines.

FIG. 7 is an upper view of the previous figure.

FIG. 8 shows an elevation of a detail at the extremity of the terminalsprovided for being stapled to the resistive track inside the body inwhich it is placed.

FIG. 9 is similar to the previous figure, showing a position prior tothe final stapling.

FIG. 10 shows a detail in cross-section of the final stapling of theterminal and the resistive track with the body or housing of thepotentiometer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The improved potentiometer hereby presented incorporates, as it may beobserved from the referenced figures of three basic components, thepotentiometer element (1), the body of anchorage (2) and the controlshaft (3).

The potentiometer element (1) comprises a body or housing (4) of apreferably square-shaped form, and of variable height having at thebottom thereof two or more protuberances (5) of reduced height andsituated in such a manner that it coincides with the zone where the endsof the resistive track (6) are to be situated, falling over the latter adouble contact of the pointer (7) which in turn, at the upper 3 onethereof, contacts the collector (8) achored in the body or housing (4).

The aforementioned pointer (7) is firmly attached to the rotor (9) whichactivated by means of the control shaft (3).

The pointer-carrier rotor (9) is attached at an upper part thereof tothe collector (8) due to the three or more riveting point by means ofplastic deformation (10), while at the lower part thereof it is guidedby a cylindrical portion (11) corresponding to the body or housing (4).The terminals (12) have the particularity of having an inside cavity(13) in order to define the bending zone of the same.

The collector (8) of laminer constitution and attached to the body orhousing (4) has a drilled part (14) such that its upper part is definedby a radius (15) which emerges over the base and continues descendingtowards the latter through an angular line. The lower angle isterminated at a bevelled portion (16).

The pointer of laminer cross-section (7) has at a central hole thereoftwo lugs (17) facing each other, whose essential particularity consistsin that the angles formed at their ends have an incisive shape in orderto enable them to be inserted in the housing (18) pertaining to therotor (9).

The potentiometer element (1) is fixed within the achoring body (2) bymeans of various lugs or rims (19) provided at an extension of walls(20) corresponding to the aforementioned anchoring body (2). Said lugs(19), having arranged the assembly, are bent by plastic deformation inorder to obtain an angular form, thus assuring the unity of theassembly. The cavities (21) and notches (22) also contribute inmaintaining the unity formed as explained above between thepotentiometer element (1) and the anchoring body (2) which inside itsanchoring cylindrical portion (23) has a diameter (24) greater than thatof the control shaft (3), thus forming in this manner a hollow or cavity(25) capable of retaining certain portion of lubricating grease.

The control shaft (3) provided for facilitating rotation of the pointercarrier rotor (9) has at an insertion end thereof a channel (26) whichlogically forms the elastic lugs (27) ended at a diameter (28) slightlyhigher than the stem (29), said diameter (28) ending at a bevelledportion (30) which cooperating with the elasticity of the lugs (27)facilitate the assembly of the control shaft pertaining thereto.

In one of the walls (20) of the anchoring body (2) an opening or window(31) is provided in order to visualize printings corresponding to thecoder or characteristics of the element.

Having sufficiently described the nature of the present invention aswell as a form of putting it into practice, it only remains to be addedthat it is possible to introduce change of form, material anddisposition in the whole invention or in parts which it comprises, aslong as said alterations do not vary substantially the nature of theinvention which is claimed as follows:
 1. A potentiometer for use inelectronic circuits in order to adjust medium and small resistivevariations, comprising:a potentiometer element located inside ananchoring body having a control shaft, wherein the potentiometer elementhas a resistive track (6) firmly attached to the bottom of a housing (4)by means of a bent extremity of the terminals (12) and by protuberances(5) which act such as elastic spring in the direction of the resistivetrack, wherein the control shaft (3) has, at an end thereof forinsertion in the pointer carrier rotor (9), a channel (26) and a slightwidening of the diameter of a stem (29) of the same, said wideneddiameter being terminated at a bevelled portion (30), the control shaftbeing removable from the pointer carrier rotor (9).
 2. A potentiometeraccording to claim 1, wherein the ends of the terminals (12) have atransversal cavity (13) provided for bending said terminals.
 3. Apotentiometer according to claim 1, wherein a collector (8) has adrilled portion (14) which at an upper angle thereof has a round shape(15) which emerges over an upper base of said collector (8) andcontinues by descending towards said base in an inclined manner, whileits lower angle or ridge has a bevelled shape.
 4. A potentiometeraccording to claim 1, wherein at least three points have been arrangedby punching through plastic deformation (10) in order for the anchoringand guiding of the upper end of the pointer carrier rotor (9).
 5. Apotentiometer according to claim 1, wherein lugs (17) of the pointer, atthe anchoring point with the rotor (9), are inserted to a housingprovided at the upper end of said rotor.
 6. A potentiometer according toclaim 1, wherein the anchoring body (2) has multiple lugs (19) extendingat its walls (20) such that when the lugs (19) are inserted in thepotentiometer element (1), the lugs (19) are pressed inwards, remainingfixed by plastic deformation.
 7. A potentiometer according to claim 1,wherein at the upper zone of the walls (20) corresponding to theanchoring body (2), multiple notches (22) are positioned which arereceived in concave cavities situated in the body of the housing (4). 8.A potentiometer according to claim 1, wherein an inside cavity (25)isarranged in a cylindrical portion (23) of the anchoring body for placinglubricant therein.
 9. A potentiometer according to claim 1, wherein anopening, capable of permitting the visualization of a printed mattercorresponding characteristics of the potentiometer, is formed in one ofthe walls (20) of the body (2).